Laminated coating



Nov. 10, 1953 A. H. DU ROSE ETAL 2,658,256

LAMINATED coATiNC Filed Aug. 7, 1952 CHROM um WIIIIIIIIIIIIII NICKELICKEL A. H. DUROSE INVHVTOR.

J D- LITTLE Patented Nov. 10, 1953 stanzas;

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Bay Village; Ohio; assignorretm The Hal-shawl Chemical Company,CleveltllipOhIlWfilBOM- ration of {Ohio Application August 7; 1952:Serial No;- 303,104

'Iliis'- invention relates'to the production of protective anddecorative-electrodeposited coata ings -on base =metals which wouldotherwise-cor rode or exhibit an unattractive appearancesMore-specifically, the invention relates-tomultiple -layer protectiveand decorative coatings adapted to be applied over'steel:orotherbasemetalibyelectrodeposition successively-from" dif ferent platingsolutions.

The most common protective anddecorative coating heretofore usedconsists of chromium-over nickel applied;. directly on the base metal toa thickness of about a thousandth of an inch or more, or'chromium overnickel applied over a coating of .copper. These nickel-ortnickel-overcopper coatings, when applied to a sufiicient thickness ;.and :builed,or when thenickelisappliedifrom a solution containing a. brightening;addition agent; are quite satisfactory for-chromium-plating. Nickel,however, is expensive-and sometimesadifficult to obtain. A needtherefore exists for a-protective and decorative coating havingsubstantially the protective anchdecorative; effect of nickel but whichcan be. produced at a lower cost and from materials which arelessaexpensive and less difficult to obtain.

Various-lmetals have been consideredras replacements for nickel, butdifficulties-rhave'alwaysz been encountered. Among the other: metalswhich have: been considered, lead is attractive from the standpoint ofcost, but is soft and-rdifflcult to buff'to a. bright finish. Antimonyalso has been seriously considered, since it is harder than lead,afiords good protectionagainst corrosion; and is readily bufied. Likenickel}. antimony will' tarnish if exposed to outside atmospheres-and;should therefore be protected. Itwanamobvious procedure to tryprotecting an antimony deposit by? applying a chromiumldeppsitathereoverin accordance with the practiceain'; nickel, 40 plating, chromium overnickel over steellbeing a very common type of coating for automobiletrim, plumbing fixtures and many other: uses. When, however, it wasattemptedztoi electrodeposit chromium on a bright (image-reflecting)antimony-surface it was found that the sresulting chromium deposit wasnot bright.

Prior tothe present invention itwasdiscovered that a bright. chromiumdeposit can beia-ppliedu over a bright antimony surfacerbyinte-rposingbetweensuchantimony surface and therchromium a very thin nickel (orequivalent) deposit. Such nickel-deposit, it was discovered could beexceedinglytthi-n, for example as thinnas-=0.00t2:s mil (0.000002 of aninch) and musttnotzbervery thick. Thenickel deposit could be produced inany of varioussnickel plating SOIlltlOllSeSllQh as the Watts bath.Deposits from the Watts'tnickel solution ona brightantimony,surfacawereafound to -be briglit up tir-a thick ness': 013 033mil. A's heavier deposit of nickel; for: example such as" normally: usedfor automobile decoration; 'tl'iat is; a dpcsit in theorder oi one' milin tliickness; was not satisfactory for use 1 between: the anti mony andchromium; Siwl'i' deposits exliibflt poop adherence; even tend' to hakeoff after tl-ie= chromium" deposit isapplied It lias nowbeen discoveredin accordance-with" the-=- present invention that in the case of the-saoove describedplating sequence, that is; chro' ium over a nickelflaslrovevbriglit antinmnw over lead or equivalent' oven-steel; ai markedly increased' resistance -to cowrosion is obtained ii at flash ofnickel-is applied to tlie steel andthem followed in turn zby leadi.b'rlglit' antimony; a nickel flash' amd chromit'n'rr;- In" other words abright l1 and" liiglily corrosion resistant -coatingis obtained by thenew of chromium over a nickel flash over brig-ht antiinony overladfirvera nickel' flash on a steel object to'-be-coated2 Tfie lad layer may beomitted if the steel is:;.mugliened before applicationof thenickelflashthereon, but the conditions are more critical and 1 results not"reliable. v

Ordinarily; the bright antimony surfacewillhave been I produced by:bufllngand then thor oughly cleaning anelec-trodeposit of antimony;the=production of which asan adherenficoating on steelis known to theart. For-example; Bloom (U3 Patent No; 2,389,131)* describes a metliodof"etching the =steel and"platingon tlie' resultingi' surface fr'om-anantimony trifluoride b'atli con tainl-ng= a= monovalent fluoride andoperating; at"

form any part of the present invention. Leach,

nickel, chromium, antimony, etc: platingare well established artsand nonovel plating; solutions" areessential to" the realization ofthe'present invention:

It the-primary object is to *form a" protective and-*decorative coating'onsteel; brass, copper-"or" the like; a" very excellent procedure isto'apply" first a flashof nickel or cobalti then an" elect'rc deposit of"lead;- tin, silveror'alloysthereof wliich' are"easily-*appliedover-nickell- A'dlierent-antialloy electrodeposits in the form ofadherent" coatings-which can -beweadily bufEd to-a high lustre: O'ntheabuitd antimony, there-maybe v tlxenaappliedz avery thin coating of:nickel; or.

cobalt, or less desirably, zinc, copperywhitesbrass: or: iron; Qverr?thee resulting: thine. depositsthere isaappliedr. amelectrodepositedacoating 2 chrov mium, suitably of a thickness of the order of 0.01 mil,which will not be dull, as in the case where it is plated directly onpolished antimony, and which will not cause a separation of the thinnickel (or the like) deposit from the antimony, as when relatively heavydeposits of nickel are applied on the antimony and followed by chromium.

So far as I am aware, no one has heretofore suggested the platingsequence herein disclosed having the protective value as aboveindicated. It is perhaps surprising that a chromium deposit would notturn out bright when applied over highly polished antimony, but that hasbeen found to be what happens; and while it would be expected fromnickel plating practice that a bright chromium deposit could be appliedon a bright nickel surface, it is surprising that an ultrathin layer ofnickel but not a heavy layer thereof would result in overcoming thetendency 2 of chromium to plate dull over polished antimony and at thesame time retain satisfactory adhesion in the case of thin layers (butnot in the case of thick layers) of nickel or cobalt. It is surprisingalso that an ultrathin layer of nickel or cobalt applied between thesteel and the lead deposit or between roughened steel and the antimonydeposit would result in extraordinarily improved corrosion resistance,far beyond what could be expected merely from the thickness of such anickel flash itself.

In the accompanying drawing, the figure is a schematic representation ofa multiple-layer deposit according to the invention, wherein thethicknesses are greatly exaggerated, and wherein the bufling step isindicated by a schematic representation of a buifing-wheel applied onthe surface which is buffed.

In the drawing, the numeral I indicates the base metal to be coated,which as indicated, may

be steel, copper brass, or the like. Electrodeposited on the base metalbody i0 is a thin layer II of nickel or cobalt which may be of athickness from 0.06 to 0.1 mil. This layer can be heavier, say up to .5mil, but it is not necessary to use any more nickel or cobalt thanindicated. Electrodeposited on the nickel flash coating is the optionallayer I2 of lead, which, it is to be understood, may be omitted ifsuitable care is taken to apply a strongly adherent coating of antimonyon the nickel or cobalt flash coating. Also the lead coating ll may bereplaced by tin or silver. The antimony deposit l3 must be stronglyadherent as it will be if applied over lead, tin or silver, and shouldbe of a thickness great enough that, upon being buffed, there is nodanger of cutting through and exposing the underlying layer. Theantimony deposit normally may be of a thickness of about 0.3 mil, andpreferably is of a thickness of the order of 0.5 to 2.0 mils. Athickness from 0.75 to 1.5 mils should prove adequate for any reasonableamount of buffing. The antimony deposit is buifed to a bright finish, asindicated by the schematic indication of a buffing wheel M in contactwith its surface, and thereafter there is applied the ultrathin coatingl5 of nickel or cobalt (less desirably copper, zinc, iron or whitebrass). This coating may be of a thickness from .001 to .05 mil, butpreferably is from 0.002 to 0.03 mil in thickness. The chromium deposit[6 is applied over the ultrathin coating I5 of nickel, cobalt or thelike and may be of a thickness from 0.001 to 0.02 mil.

While the nickel flash under chromium and over bright antimony on leadon steel is not per se a part of the present invention, the fact thatits deleterious effect on corrosion resistance can be overcome by aflash of nickel between the steel and the lead is believed not to haveknown heretofore. The effect is marked and goes beyond any mere additiveeffect of the thin nickel coating. It was found for example that .01 milof chromium on 1.0 mil of antimony (buffed) on .2 mil of lead on steelexhibited a salt spray resistance of 100 hours but was not bright.Applying .003 mil of nickel or cobalt over the buffed antimony and underthe chromium gave good brightness and adherence but the salt sprayresistance was reduced to 40 hours. Applying .06 mil of nickel betweenthe steel and the lead in addition to the nickel flash between theantimony and the chromium, the salt spray resistance went up to 100hours. This amount (0.06 mil) of nickel on steel as the only coatingwould resist salt spray only from 2 to 4 hours.

Cobalt in similar thicknesses was found to be the equivalent of nickelfor the flash on the steel except for its higher cost.

Plating solutions suitable for the electrodeposition of antimony, lead,nickel, cobalt, zinc, iron,

copper and white brass are as follows:

(1) SbFs 250 g./l. NHiF 200 g./l. pH 4.5 Temperature 130 F.

(2) SbF3 NH4 2S04 400 g./l. pH 1.5 Temperature 130 F.

(3) Pb(BF4)2 33.5 oz./gal. HBF4 10.7 oz./gal. H3130: 3.0 oz./gal. Glue.03.06 oz/gal. Temperature Room (4) NiSO4.6H2O 250 g./l.

NiC12.6H2O 35 g./l.

H3303 35 g./l. pH 4.0 Temperature 120 F.

(5) NiS04.6H2O 100 g./l.

NiClz.6HzO g./l. H3303 g./l. pH 3.0 Temperature Room The antimon surfacemust be well cleaned before nickel is applied.

(6) C0Cl2.6H2O 100 g./l.

NH4F.HF 20 g./l. pH 3.0 Temperature 130 F. ('7) ZI1(CN)2 g./l. NaCN 42g./l. NaOH 79 g./l. NazS 0.75 g./l. Temperature 80 F. (8) FeSO4.7H2O 200g./l.

NaBFi 40 g./l. pH 3.0 Temperature F. (9) CuCN 22 g./l. Free Cyanide 7.5g./l. Water Remainder pH 12 Temperature F. (10) Zn(CN)z 60 g./l. Cu(CN)214 g./l. NaOH 60 g./l. NaCN 52 g./l. NazSOa 0.48 g./l. Temperature 90 F.

Having thus described the invention, what is claimed is:

1. A process comprising electrodepositing on a metallic surface of theclass consisting of steel, brass and copper a layer of a metal of theclass consisting of nickel and cobalt and mixtures thereof of athickness from .02 to .2 mil, forming on said layer an adherent coatingof a metal of the class consisting of lead, tin and silver, said coatingbeing applied by electrodeposition, forming on said last mentionedcoating a bright coating of electrodeposited antimony, forming on saidbright antimony coating a film of a metal of the class consisting ofnickel, cobalt, zinc, iron, white brass and copper of a thickness from.001 to .05 mil, said film being applied by electrodeposition, andelectrodepositing a layer of chromium over said film.

2. A process comprising electrodepositing on steel a layer of nickel ofa thickness from .02 to .2 mil, forming on said layer of nickel anadherent coating of lead, said coating being applied byelectrodeposition, forming on said last mentioned coating a brightcoating of electrodeposited antimony, forming on said bright antimonycoating a film of nickel of a thickness from .001 to .05 mil, said filmbeing applied by electrodeposition and electrodepositing a layer ofchromium over said film.

3. A process comprising electrodepositing on a metallic surface of theclass consisting of steel, brass and copper a layer of a metal of theclass consisting of nickel and cobalt and mixtures thereof of athickness from .02 to .2 mil, forming on said layer an adherent coatingof a metal of the class consisting of lead, tin and silver, said coatingbeing applied by electrodeposition, forming on said last mentionedcoating a bright coating of antimony, said coating being applied byelectrodeposition and then buffed to brightness, forming on said brightantimony coating a film of a metal of the class consisting of nickel,cobalt, zinc, iron, white brass and copper of a thickness from .001 to.05 mil, said film being applied by electrodeposition andelectrodepositing a layer of chromium over said film.

4. A process comprising electrodepositing on steel a layer of nickel ofa thickness from .02 to .2 mil, forming on said layer of nickel anadherent coating of lead, said coating being applied byelectrodeposition, forming on said last mentioned coating a brightcoating of antimony, said coating being applied by electrodeposition andthen bufied to brightness, forming on said bright antimony coating 2.film of nickel of a thickness from .001 to .05 mil, said film beingapplied by electrodeposition and electrodepositing a layer of chromiumover said film.

5. A laminated, metallic, bright, protective coating on a metal base ofthe class consisting of steel, copper and brass consisting of a firmlyadherent layer of a metal of the class consisting of nickel, cobalt andmixtures thereof of a thickness from 0.2 to .2 of a mil, a layer of theclass consisting of lead, tin and silver of a thickness from 0.1 to .7mil overlying and adherent to said last mentioned layer, a firmlyadherent layer of antimony on said last mentioned layer and having abright surface, a film of a metal of the class consisting of nickel,cobalt, zinc, iron, white brass and copper of a thickness from .001 to.05 mil firmly adherent to said bright surface and a layer of fullybright, unburied chromium of a thickness from .003 to .03 mil firmlyadherent to said film.

6. A laminated, metallic, bright, protective coating on steel consistingof a firmly adherent layer of nickel of a thickness from .02 to .2 mil,a layer of lead of a thickness from 0.5 to .7 mil overlying and adherentto said last mentioned layer, a firmly adherent layer of antimony of athickness from 0.0003 to 0.002 of an inch on said last mentioned layerand having a bright surface, a film of nickel of a thickness from .001to .05 mil firmly adherent to said bright surface and a layer of fullybright, unbufied chromium of a thickness from .003 to .03 mil firmlyadherent to said film.

ARTHUR H. DU ROSE. JOHN D. LITTLE.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,314,603 Mott Sept. 2, 1919 1,738,748 Wirshing et al. Dec.10, 1929 1,792,082 Fink Feb. 10, 1931 1,918,159 Weisberg et al July 11,1933 2,039,068 Domm Apr. 28, 1936 2,428,033 Nachtman Sept. 30, 1947

5. A LAMINATED, METALLIC, BRIGHT, PROTECTIVE COATING ON A METAL BASE OF THE CLASS CONSISTING OF STEEL, COPPER AND BRASS CONSISTING OF A FIRMLY ADHERENT LAYER OF A METAL OF THE CLASS CONSISTING OF NICKEL, COBALT AND MIXTURES THEREOF OF A THICKNESS FROM 0.2 OF A MIL, A LAYER OF THE CLASS CONSISTING OF LEAD, TIN AND SILVER OF A THICKNESS FROM 0.1 TO .7 MIL OVERLYING AND ADHERENT TO SAID LAST MENTIONED LAYER, A FIRMLY ADHERENT LAYER OF ANTIMONY ON SAID LAST MENTIONED LAYER AND HAVING A BRIGHT SURFACE, A FILM OF A METAL OF THE CLASS CONSISTING OF NICKEL, COBALT, ZINC, IRON, WHITE BRASS AND COPPER OF A THICKNESS FROM .001 TO .05 MIL FIRMLY ADHERENT TO SAID BRIGHT SURFACE AND A LAYER OF FULLY BRIGHT, UNBUFFED CHROMIUM OF A THICKNESS FROM .003 TO .03 MIL FIRMLY ADHERENT TO SAID FILM. 